The branch of science which studies the interactions among organisms and between organisms and physical environment is called as

Options

A. Ecology
B. Ecosystem
C. Phytogeography
D. Ethology

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the branch of science that studies the interactions among organisms and between organisms and their physical environment.

2. **Identifying Key Terms**: The key terms in the question are "interactions among organisms" and "physical environment". This implies a focus on how living organisms relate to one another and their surroundings.

3. **Evaluating Options**:
- **Option 1: Ecology**: This is the study of ecosystems, which includes both biotic (living organisms) and abiotic (physical environment) components. It focuses on how organisms interact with each other and their environment.
- **Option 2: Phytogeography**: This field studies the distribution of plant species and does not encompass the broader interactions among all organisms and their environment.
- **Option 3: Ethology**: This is the study of animal behavior, particularly in natural conditions, but it does not cover the interactions of all organisms or their physical environment.
- **Option 4: (Not provided)**: Assuming it is another unrelated field, it would not be relevant.

4. **Selecting the Correct Answer**: Based on the evaluation, the correct answer is **Option 1: Ecology**, as it encompasses the study of interactions among organisms and between organisms and their physical environment.

5. **Conclusion**: Therefore, the branch of science that studies these interactions is called **Ecology**.